Apparatus for disintegrating and classifying dry materials



Sept. 11, 1956 H. G. LYKKEN ETAL APPARATUS FCR DISINTEGRATING AND CLASSIFYING DRY MATERIALS 4 Sheets-Sheet 1 Filed Dec. 26, 1952 Sept. 11, 1956 H. G. LYKKEN EI'AL APPARATUS FOR DISINTEGRATING AND CLASSIFYING DRY MATERIALS 4 Sheets-Sheet 2 Filed Dec. 26, 1952 5 m w m m HENRY G LYKKE/V 7750/; A. 9025/4 WM AYM A TTOFPNEYS p 11, 1956 I H. s. LYKKEN ETAL 2,762,572

APPARATUS FOR DISINTEGRATING AND CLASSIFYING DRY MATERIALS Filed Dec. 26, 1952 4 Sheets-Sheet 3 v INVENTORS fifE/VRY G. LY/f/fE/V 7 509 A. POZSA A 7- TOR/Vt; v.5

Sept. 11, 1956 Filed Dec. 26, 1952 H. G. LYKKEN ETI'AL 2,762,572

APPARATUS FCR DISINTEGRATING AND CLASSIFYING DRY MATERIALS 4 Sheets-Sheet 4 I m g INVENTORS fi/ENRY G. LYKKEN 7750/? A. 902% ATTORNEYS as scavenging.

United States Patent APPARATUS FOR DTSIN'IEGRATING AND CLASSIFYENG DRY MATERIALS Henry G. Lykken and Tibor A. Rozsa, Minneapolis,

Minn., assignors to The Microcyclomat Co., Minneapolis, Minn., a corporation of Delaware Application December 26, 1952, Serial No. 328,016

15 Claims. ((11. 241-49) This invention relates to an apparatus for disintegrating materials in the dry state and for classifying the disintegrated particles in an integrated operation. Inreducing any dry material to a range below 100 mesh and particularly to the sub-sieve sizes, it is essential, for most Operations, to remove the finished sizes progressively and completely from the grinding zone as soon as they are produced. If the finished sizes are not completely segregated and promptly removed, inefficiency in the milling operation will ensue, not only due to reduction beyond the desired size particles, but also due to the cushioning effect of the finer material in the charge. The removal of the desired size and smaller may be designated The difference between a poor scavenging of a mill producing particles of particular sizes or complete and eifective scavenging may, and frequently does, make a difference of 200 to 300% in grinding efiiciency, particularly in the finer ranges. If material reduced to the desired fineness is not promptly withdrawn from the mill charge it is subjected to continuing reduction at increasing cost. Such further reductions are in many cases undesirable since in a large number of grinding operations the particles of a specified size, with a minimum of superfines, may be desired. For example, sugar for chocolate coatings should preferably be ground to 30 microns with a minimum content of superfines.

In the milling of clays, kaolin, talc, natural pigments, graphites, etc. the wanted material is soft. They are lighter and reduce to fine particle sizes much more readily than does sand, silica, grit and harder gangue materials that are present in deposits of such substances in nature. In this'instance, the problem is to eliminate the contaminating material with little or no reduction, returning only the yet unreduced wanted softer material to the feed for further reduction.

In the milling of heat sensitive materials, such as DDT, cocoa, and many natural and synthetic resins, little heating is tolerated due to increasing resistance to reduction as the temperature rises. In the case of many materials, grinding can be effected only at very low temperatures.

This calls for precooling the mill feed, often to a Very low temperature, then reducing the material progressively. As it first enters the mill, it will reduce until its temperature reaches a point of excessive resistance to further reduction. The fines must then be progressively and continuously removed as well as the whole mill charge before its temperature becomes excessive. The oversize is then precooled and returned to the feed for further reduction in a continuing cycle.

In many grinding operations involving mixed materials of varying specific gravity or degrees of grindability, or materials like seeds and grains having fibrous portions that must be removed from the product, a multiple stage or step operation is required. The material fed to the first unit is only partially reduced as it enters the classification chamber where the fines of any desired maximum particle size may be removed for separate treatment and the remaining oversize scavenged off for further reduc- 2 tion in a second milling unit with or without intermediate treatment or processing by other means.

It is an object of the present invention to provide ap paratus which will meet all the requirements for milling and size separation or scavenging above recited and to provide apparatus of highest possible efiiciency in respect to particle reduction.

It is another object of the invention to provide apparatus having maximum possible precision in particle sizing in respect to the mill product produced.

It is a further object of the invention to provide for the reduction of material to any degree of fineness with a minimum of superfines and to make possible the reduction of heat sensitive materials to any degree of fineness at minimum cost.

It is a further object of the invention to provide apparatus by which unwanted hard or dense materials occurring in natural substances may be separated from the wanted portion.

It is also an object of the invention to provide an apparatus for the reduction and classification of materials and readily adapted to a wide variety of purposes, materials, particle size reduction and classification.

Another purposeof the invention is to provide a threestage method of classification to insure a more complete and precise particle size segregation in which the mixture of material to be classified is first subjected to an instance air jet induced vortex action by a non-rotating unidirectional. vortex inducing means which eliminates the coarser material and/or keeps it away from theperiphery of the secondary rotating classifier; a second rotating classifier of the centripetal type into which only the fines and near fines can enter and only the fines or wanted size can pass through, the oversize being rejected; and a third combination of means for sifting out any fines that may escape through the classifier zone and return same with theair to the classifier zone.

The invention is further illustrated with reference to the drawings in which corresponding numerals refer to the same parts and in which:

Figure'l is a vertical sectional view of an exemplary form of the milling and classifying apparatus of the present invention;

Figure 2 is a horizontal sectional view taken along the line and in the direction of arrows 2-2 of Figure 1;

Figure 3 is a horizontal sectional view taken along the line and in the direction of arrows 33 of Figure '1;

Figure 4 is a horizontal sectional view taken along the line and in the direction of arrows 4-4 of Figure 1;

Figure 5 is a vertical sectional view of a slightly modified form of apparatus of the present invention;

Figure 6 is a horizontal sectional view taken along the line and in the direction of arrows 6--6 of Figure 5.

Referring first to Figures 1-4, the exemplary form of apparatus shown in these figures consists of a unitary vertical milling and classifying device together with a mounting base. The apparatus is divided generally into a structure or platform 10, a base 11, a classifying section 12, milling section 13 and a top cover and feed housing 14. Into the base 11 there is inset a fan structure 15. The structure or platform 10 usually consists of a circular or oblong platform having side walls 20 and having a floor flange 21 by which it may be fastened down. The platform 20 is usually extended out to one side sufiiciently so as to serve as a mounting for a vertical shaft motor having a downwardly projecting shaft extension reaching into the structure 20. The structure 20 usually has a cover at 22 which serves as a mounting for the bearing 23 which is held in place by ring plate 24 fastened by the bolts 19.

Upon the platform, shown opposite the bracket 10, there is mounted the mill base 11 which is usually acylinder of heavy plate 25 having a lower flange 26 and an upper flange 27. The mill base has a wide window 28 at one side or opposite sides which forms an opening or openings 29 for servicing the bearing assembly 23. The fan structure 15 will be referred to in further detail hereinafter. Upon the flange 27 of the mill base there is mounted a ring plate 30 having a central aperture 31, and upon the plate 30 there is mounted a heavy sheet metal cylinder 32, the cylinder being welded to the plate 30 as indicated at 34. To the upper end of the cylinder 32 there is provided a flange 35 that is welded in place at 36 to the cylinder, the flange forming a mounting by means of which the lower flange 37 of the mill structure 13 may be bolted in place by means of the bolts 38. A ring plate 39 is bolted between the flanges 35 and 37 for mounting another part of the classifier 12, as will presently be described. The flange 37 is welded at 33 to a cylindrical housing 40 of the mill which likewise has the flange 41 at its upper end to which there is bolted the upper closure plate 42.

The upper closure plate is provided witha wide aperture at 4445 over which there is positioned an inlet box 47. The inlet box has a slide gate 48 at one end which, when open, permits the entrance of atmospheric air into the box. The box 47 may also be provided with one or more inlet pipes 49 which return by means of pipes 50, 51 and 52 to the skimmer boxes 54 and 55 which will be described in greater detail. Through the box 47 there also projects a tubular inlet 56 by means of which the solid material to be disintegrated is fed into the mill structure.

The upper plate of the box 47 serves as a mounting for the bearing structure generally designated 60. The details of the construction of the bearings 23 and 60 are within the province of mechanical design and need not be further explained here except to state that the bearings are preferably of the ball or tapered roller type and they are adequately sized to carry the rotor of the mill and classifier structure at the speeds desired, and are adequately protected against the entrance of abrasive material into the bearings. Upon the bearings 23 and 60 there is mounted a shaft 61 for rotation concentrically with the axis of the entire mill and classifier structure. The shaft 61 is provided with a shoulder at 62 a slightly reduced diameter threaded portion 63 and a reduced diameter end portion 64 at its upper end. It is similarly provided with a shoulder at 65 and a reduced diameter step 66 on which the bearing 67 is seated, the bearing being held in place by a combined ring nut and oil shield 68 that is threaded on the shaft at 69, the lower reduced end 70 of the shaft 61 projects out through the oil seal 71 and is provided with a keyway 72. A pulley is mounted upon the downwardly projecting end of the shaft 70 and is belted to a motor which may be mounted on the same platform 20 which serves as a mounting for the mill and classifier structure. The upper bearing inner race 73 is pressed on the upper end of the shaft. The bearing 74 is preferably of the self-aligning type.

The shaft 61 is enlarged and reinforced by a tube 80 secured to the shaft by the end closure 84 at the top and the end closure 81 at the bottom, the shaft 61, closures 81 and 84 and tube 80 being welded into a unitary structure. All rotative elements are mounted on and driven by the tube 80.

The lower or exhaust fan disk 76 of the impeller fan unit 125 is bolted to the end closure 81 by cap screws '82 and serves as one end plate upon which remaining 4 fan hub and closed end fan unit 140142, the disk 155 and the rotating centripetal classifier unit 150.

The grinding units 170 to 174 are mounted and keyed directly to the axial tube and the top fan unit 85 is bolted to the top enclosure 84 by means of cap screws 88 and is drawn down to hold the stack in tightly assembled relation.

Referring to Figure 3 the channels (formed by spaced segmental blocks 77 of the impeller unit) join to the spaces 101 and thence to the channels 102. The structure of plates 77 and 96, together with the intervening segment 77 accordingly form a fan impeller 125 which when rotated causes the movement of gaseous fluid downwardly through spaces 100 and 101 in the direction of arrow 126 (Figure 1) and thence outwardly in the direction of arrows 103 (Figure 3). A scroll housing is provided around this fan impeller, said housing being composed of an outer spiral plate 104, Figure 3, of gradually increasing radius in the clockwise direction from the point 105 to the point 106, the housing being provided with an outlet tube 107 presenting the outlet opening 108. The lower plate of the housing at 110 is cut through the side wall 25 of the mill base 11 and is welded to it and adaquately braced at various points by means of the angle gussets 111. The upper plate of the housing is composed of a spiral ring 112 upon which there is mounted an inner concentric ring 114. The space between the plate 110 and the lower plate 76 of the fan structure is filled by a solid filler block 115 held in place by the rivets 116. A slight running clearance space at 117 is allowed. Similarly, the space between the lower surface of the concentric plate 114 and the upper plate 96 is filled by the spacer block 118, likewise held in place by the rivets 120. Again, slight running clearance is provided at 121. The block 118 is rounded oif at 122 connecting to the clearance space 121, it being noted that the spacer 118 is smoothly curved adjacent the curved portion 98 so as to maintain uniform clearance.

The impeller of the fan, here generally designated 125, when it is turned causes a full flow of gaseous fluid in the direction of arrows 126126, Figure 1, and thence outwardly in the direction of arrows 103, Figure 3, into the scroll housing 104 as indicated by the arrow 128 and outwardly as shown by arrow 129 through the housing 108. At the same time a slight flow may occur in the direction of arrows 130 through the clearance space 121 and a slight flow may occur at 131 through the clearance space 117. These slight flows of air are from the uncontaminated source of air within the base 11, as supplied through the window 29 and window 75, and hence no contamination occurs in respect to the sized material delivered by the impeller 125 into the scroll 104 and out through opening 108.

The centripetal classifier unit generally designated 150, is here illustrated as composed of a plurality of disks 151-151 having radial slots at 151A and a pair of end disks of somewhat thicker stock at 152152, likewise slotted at 152A. The slots receive radial blades, the blades being solid throughout the portion of the slots 151A-152A. The back parts (radially inward edges) of the blades 153 are slotted in turn at 153A to receive the inner parts of the rings 151 and 152. The whole assembly is thus dovetailed so as to provide a structure made up of the rings 151 and 152 that are held in spaced relation by the radially arranged blades 153, see Figures 1 and 2. The structure 150, as an assembly, is fastened together by welding or fusion brazing, and is then mounted at its lower surface against the plate 155 to which it is held by the cap screw 154 and enters through the small ring flange on the hub 140. A tubular screen is provided at 196 when required. The upper surface of the assembly is capped by the plate 156 likewise held in place by the cap screw 157. It is noted that the plate 156 extends out to within a short distance of the inner surface of the wall 40, thus leaving an annular space at 158 through which a downflow of pulverized material and gaseous fluid may pass, The plate 155 extends preferably out well beyond the assembly 150 so as to be close in proximity to the lower edge 160 of a pendant wall generally designated 161. A space at 162 is also provided between the top surface of the plate 155 and the lower edge of the pendant wall 161. The wall 161 is provided with a flange 163 at its upper surface by means of which it is attached by screws or welding to the under surface of the ring 39. The pendant wall 161 is itself punched or assembled to provide a plurality of louvers as shown in Figure 2 or 6. In Figure 2 these louvers are punched from a sheet metal, inwardly and in a direction generally tangentto the circular aspect of the pendant wall. The louvers slant in the direction of rotation of the rotary unit of the mill, the direction of rotation being shown by the arrow 164, Figure 2. There are thus provided a plurality of slots 165 through which an inflow of gaseous fluid under pressure may pass, as indicated by the arrows 166. The pendant wall 161 may also be constructed of a plurality of separate plates positioned as shown in Figure 6 and mounted between upper and lower ring flanges to which the plates are attached by welding or brazing. Either form or other equivalent forms may be used.

The inner surface of the plate 156 rests on the upper edge 91 of the radial vanes 92, Figures 1 and 2, which act as spline members, and upon the upper surface of plate 156 there is positioned a stack of milling stages 170-174 between which, in the exemplary form shown, there are provided vibratory disk assemblies 177. The milling stages are similar and hence only the lower one 170 will be described. Thus, stage 170 has a hub 1170A to which a plate 175 is attached. The plate 175 carries a plurality of radial vanes 176. Between successive milling stages are mounted vibratory plates 177 which are spaced from the radial vanes 176 so as to be free to vibrate. In other mills, the plates 176 may be clamped tightly between the milling stages. In other cases the vibrating plates may be omitted as in Figure 5.

Upon the uppermost stage 174 of the grinding section 13 of the mill there is superimposed the plate 85 which, as previously stated, is drawn down by the cap screws 88 and also by the washer 179 which, in turn, is pushed down firmly by the ring nut 180 threaded on the threads 63 of the shaft 61.

Upon the cylindricd shell 32 of the classifying section of the apparatus there are provided one or more skimmer boxes 54 and 55 which may be constructed as shown in the copending application of Henry G. Lykken, Serial No. 278,239, filed March 24, 1952. Each of the skimmer boxes has one or more adjustable wire lips 1&1, the

edge of which is directed against the spiral flow of gaseous vapors in the mill, which carry the pulverized dry solids, i. e. the lip 181 is directed against the direction of rotation, arrow 164, Figure 2, 128, Figure 3. Pipe connections may, if desired, be made to such of the skimmer boxes 54-55 as are used and, if desired, are connected through pipes 51, 52 and 50 to thenipple 49 of the feed box 47.

On the under surface of the plate 30 at the bottom of the classifying section .12 there are provided a pair of opposed spaced guides 185-185, Figures 1 and 4, which serve as slideways in which the opposed dampers 182- 182 may slide. The dampers are cut out at their center along the semi-circular lines 183-183 to fit the outer diameter of the tubular member 99 and may, if desired, be provided with edging strips 184 so as more effectively to seal against the cylindrical portion 99. The dampers may be withdrawn to any desired position, such as that illustrated in Figure 4, so as to vary the inlet area through the opening 31, whereby the amount of air or other gaseous fluid that is introduced through that opening and moved into the classification chamber .12 by the fan 136-137, may be accurately controlled with respect to the amount of air or gaseous fluid introduced via the fan 85-86.

In operation solid material to be ground is introduced by means of the feed pipe 56 through a screw feeder or any other feeding device for solids. The solids are preferably pre-broken somewhat for ease of feeding. The feeder is preferably of the type which does not also allow the introduction of gaseous fluid (such as air). The solid material simply falls down upon the spinning fan plate having the vanes 86 thereon and is distributed.

The solid material is accordingly thrown centrifugally outwardly against the upper portion 40A of the mill casing 40, whereupon in falling downward it is subjected to action produced by the milling sections 170-174 and is progressively reduced in size as it moves downwardly. Some feed of air or other gaseous fluid may be introduced by opening the damper 48 so as to allow a certain amount of gaseous fluid to move through the milling section and to balance the pressure therein. In some instances, as where the coarse particles are recycled from the skimmer boxes 54-55 into the nipple 49 in the feed box, some gaseous fluid will thus be introduced. All of the feed, including the solid material introduced via pipe 56, any flow of gaseous fluid and coarse particles introduced via pipe 49 and any gaseous fluid permitted to enter via gate 48 of the feed box, are introduced through the opening 44-45 and thence distributed by the fan 85-86 into the interior of the milling section 13. This constitutes the feed.

All of the disintegrated material passing downwardly through the milling section is delivered along with the gaseous fluid portion of the feed through the annular orifice 158 which, it will be noted, is immediately inside the pendant wall 161. This flow consists of. a mixture of coarse and fine particles in gaseous fluid suspension.

The action of the classifying section is as follows: The downflow of gaseous fluid and pulverized granular material of mixed sizes at 158 is balanced to some extent by the inflow of gaseous fluid through the opening 31 and most gaseous fluid entering the classifying section 12 via 153 and opening 31 is withdrawn through the assembly 150 (or the equivalent assembly such as that of Figure 5) and thence into the channels -100 (which extend axially through the rotary unit) and the flow then continues and in the direction of arrow 126 (Figure 1) and thence out through the impeller of the fan.

Within the classifying unit 12 there is a'complexmultiple phase classifying action. The fan 137- (Figure-1) produces a tight spiral or vortex of air (or other gaseous fluid) in the space 197. The spiral is generally upward. In addition, the radial blading 144 produces a plurality of tight spirals within each blade intensifying the vertical spiralling action against the inner surface of the cylindrical wall 32. All of the gaseous fluid is thus maintained in a very strongly disturbed vorticular condition within the space 197 with the solids continuously disturbed. The coarser particles are more generally against the wall 32 where they may be picked off as desired by the skimming wiers 181-181 of the skimmer boxes 54-55 at different levels. Any fines and near fines that may get into the space17 with rejects and most of the gaseous fluid in that space, in order to leave the classifying section at all, must pass inwardly through pendant wall 161 and then through the centripetal classifier assembly 150. 'In progressing thus through the wall 161 and towards the assembly the gaseous fluid and its load of fines and near fines is drawn inwardly as in the direction of arrows 166-166 (Figure 2) through the louvers of the pendant wall 161. At the same time within the pendant wall 161 there is again a spiral downflow from the annular orifice 158, this spiral downflow being sustained by the assembly 150 and such feed through 158 contains coarse as well as fine solid materials. The inwardly directed air under pressure from air inlet fan passing through the louvers in the direction of arrows 166, blasts through the spiralling downflow which is inside of the pendant wall,

and entering from the annular orifice 158, this being illustrated by the crossed arrows 166-166 and arrow 191 of Figure 2, and a vorticose cross flow action of great intensity is thus established inside the pendant wall. At the same time the radial vanes 153 of the centripetal classifier unit 150 in each instance produce small vortices 194, Figure 2, somewhat within the peripheral limits of the radial blades and the intervening rings 151-151. In addition, there is a general velocity (arrow 195, Figure 2) into the narrowing space between adjacent radial blades 153 and through the restriction, here illustrated as a screen 196. Depending upon the speed of operation and physical constants a certain range of finer particles are moved inwardly under these actions into the axial spaces 100 of the rotor, the coarser particles being meanwhile thrown outwardly against the pendant wall 161 where they gradually move spirally downwardly to the bottom of the wall, whereupon they are thrown out through the space 162 into space 197, by the action of the whirling plate 155. There the coarse particles and anyfines that may have adhered to them are met by the outer vortex and spiralling upflow in the space 197, as previously described. Thus, the larger particles are dusted off, the fines and near fines being carried up and again given a chance to be pulled in through the louvers of the pendant wall 161 through the vortices 194 and in the direction of arrows 195 into the spaces 100.

In this way there is provided a three-fold classifying efiect, i. e., that classifying efiect which is due to the centripetal classifier 150, that effect due to the pendant wall construction 161 and finally the classification occurring in the space 197 which is the combined effect of the fan bladings 137, 144 and the spatial arrangements. In this way the coarse particles, which in the main congregate against the inner surface of the cylinder 32, are freed from adherent fines and near fines and the coarse particles are then removed by the skimmer boxes 5455 as they are separated and may be discarded, used or recirculated, as desired in the operation.

Thus, in the milling of many clays containing silica, the silica resists disintegration while the clay itself more readily disintegrates. This is an advantage, when utilizing the instant invention, since the larger particles of resistant silica are thus capable of being separated from the lighter more easily reduced clays by withdrawal of the larger and heavier silica, etc. from the bottom of the classifier chamber and withdrawal of the lighter material at a higher level for further reduction.

In other instances, as in the disintegration of grains, the mill may be adjusted so as to produce only a primary break for removing the tough bran-like outer coatings of the grain or hull structure. These likewise may be separated and removed at dilferent levels before progressively further milling the grain material.

In other instances, as in the milling of plastics the larger particles not reduced in size, may readily be removed from those that are of fine size, and the charge refrigerated before being recirculated or passed to a second mill.

Referring to Figure 5, the construction is similar to that shown in Figure 1 with the exception of the following particulars, which are illustrative of variations that may be utilized. The fan section generally designated 15 of Figure 5 is provided with a spacer block at 200 fastened to the lower plate 201 while the spacer block 202 and the cover plate 203 are fastened by means of cap screws 204 to the lower plate 205 and thus rotate with it. In addition, a smaller spacer 206 fastened to the inner annular plate 207 is provided so as to leave a small clearance space 208, another small clearance space being at 209. The classifying section is constructed in generally the same manner except that unit 150 of Figure l is here replaced the whole unit being held down by the clamping plate 214. It may be noted parenthetically that the form of classifier unit 150 or 200 may be replaced by any of the forms shown in the copending application of Henry G. Lykken, Serial No. 306,126, filed August 25, 1952. Here the unit 210 provides a plurality of narrow spaces 215 through which the flow of gaseous fluid and separated fine material passes. In Figure 5 also the pendant wall 220 is composed of a plurality of separate plates 221, as shown in Figure 6, the same being notched at the bottom to receive a retaining ring 222 and fastened at the top by welding or mortising to the plate 223. In the milling section a plurality of separate liners are illustrated of varying heights. Thus, the tallest liner 224 reaches from plate 223 upon which all of the liners rest to the diaphragm plate 225. The next liner 226 reaches only to the bottom of the upper grinding stage 227. The next lower liner 228 reaches to the bottom of the grinding stage 229 and the shortest liner 230 extends only from the plate 223 to the bottom of the second grinding stage 231, the lower grinding stage being shown at 232. The grinding stages are made of successively slightly smaller diameters and in this milling section also the separating disks are eliminated between successive grinding stages. In addition, a plurality of shims at 234 are illustrated. In many milling operations it is desirable to change the number, height or shape of the grinding stages, and these may be restacked and selected at will and clamped up on the rotor composed of the shaft 61 and the tube 80. In the same way the classifying unit 150 of Figure l or 210 of Figure 5 may be selected from among those herein illustrated, or from those illustrated in the aforesaid application of Henry G. Lykken, Serial No. 306,126, filed August 25, 1952. In the illustrated form of the invention the shaft 61 is provided with rugged end plates 235 and 236 which are welded in place as by the weld 237 and 238. The tube is then pressed on and welded in place,

the whole forming a rugged and stiff rotary member. In addition, the vanes or splines 92 may be welded in place on the tube 80 throughout the length desired for centering as many of the units as is required throughout the length of the rotary unit having the longitudinal channels 100, see Figure 2. The skimmer box 240 operates on the same principle as that illustrated in the copending application of Henry G. Lykken, Serial No. 278,239, filed March 24, 1952, and may be mounted on a separate plate 239 so that its efiective edge can be moved vertically, thereby allowing a selective skirrmiing effect.

The invention may, as an example, be constructed essentially as a classifier with little or no grinding effect on the larger particles and largely for the removal of finer material only. It may be adapted for use in series with reducing means of other types and principally as a classifier.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments herein.

What we claim is:

l. A mill for disintegrating and classifying dry solid material comprising a vertical cylindrical casing having a grinding zone in its upper portion and a classifying zone at a lower portion, a closure at the top having at least one inlet and a closure having an annular opening at the bottom, a rotor journalled for rotation in the casing, said rotor projecting downwardly through and below said annular opening, grinding means on said rotor in the grinding zone and classifying means in the classifying zone, a fan on said rotor having radial passageways, longitudinal passageways in said rotor leading from the classifying means downward connected to said radial fan passageways in the rotor at the lower end thereof, a housing enclosing said radial fan passageways forming a fan housing, said housing being spaced from said bottom closure having said annular opening to provide an air inlet to the annular opening.

2. The apparatus of claim 1 further characterized in that a fan is provided on said rotor in the classifying zone of said cylindrical casing, said fan being adjacent the annular opening for drawing gaseous fluid through the opening into said classifying zone.

3. A mill for pulverizing and classifying dry solids comprising a vertical cylindricalcasing having a grinding zone in its upper portion and a classifying zone of larger diameter in a lower portion with closures at the top and bottom, at least one inlet in the top closure and an annular opening in the bottom closure, a rotor journalled for rotation in the casing, said rotor projecting down wardly through said annular opening and terminating in an enlarged fan portion, grinding means in the grinding zone of the casing and classifying means in the classifying zone, longitudinal passageways extending axially through the rotor from the classifying means and connecting to the fan portion of the rotor, a housing around said fan portion, said housing being spaced from the annular opening so as to provide a passage space thereto for gaseous fluid, an air inlet fan within the classifying zone of the casing adjacent the annular opening above said bottom, an annular passageway between the grinding zone and the classifying zone of said casing, a plurality of spaced radial apertures extending from the periphery of the rotor to the longitudinal passageways in the rotor of the classifying zone, means in said zone for fluidizing and circulating solid material and means in the peripheral Walls of the zone for withdrawing material circulating on the wall.

4. The apparatus of claim 3 further characterized in that a pendant wall is provided in said classifying zone outside said annular passage but spaced from the classifying zone wall, said pendant wall being provided with tangential openings therethrough extending inwardly and in the direction of rotation of the rotor.

5. The apparatus of claim 4 further characterized in that an annular ring is provided on the rotor below said pendant wall and extending outwardly in slightly spaced relation from the bottom of said wall.

6. The apparatus of claim 5 further characterized in that additional fan means is provided below said annular ring and above the air inlet fan adjacent the annular opening.

7. The apparatus of claim 3 further characterized by embodying a multi-stage classification system comprising a circular non-rotative pendant Wall vortex inducing means, a rotatable centripetal classifier concentrically within said vortex inducing means, and below the discharge of oversize material from said centripetal classifier, further fan means for fluidizing said material and maintaining said material in an outer vortex whereby the finer fractions may be withdrawn inwardly with the fiuidizing and scavenger air through said non-rotative pendant wall vortex inducing means.

8. A mill for pulverizing and classifying dry solids comprising a vertical cylindrical casing having an upper portion of smaller diameter and joined to a lower portion of larger diameter, said upper portion constituting the grinding chamber and the lower portion the classifying chamber, a cover across the top of said upper portion having an inlet thereinto for solid material to be ground and classified and for entrance of gaseous fluid, a closure across the bottom of said classifying zone having an annular opening therein, a rotor journalled in said casing, said rotor extending downwardly through said grinding zone and classifying zone and projecting downwardly through and below said annular opening, the portion of said rotor in said grinding zone being provided with means for disintegrating solid material, a diaphragm across said casing separating the grinding and classifying zones, said diaphragm being of a size such as to leave a narrow annular passage between the diaphragm and the grinding zone Wall at the bottom of the grinding zone,

said rotor having at least one axial passageway extending from the level of the classifying zone and thence downwardly through and below said annular opening, said rotor being provided with an enlargement of increased diameter at its lower end, said enlargement having spaced radial passages therethrough connected to said axial opening and forming a fan portion, a housing closing said fan portion, said housing having an outlet opening, said housing being spaced-from and below said annular opening so as to form an inlet into which gaseous fluid may enter for passage to and through the annular opening, said housing being closely fitted around the rotor on the side adjacent the annular opening, a cylindrical wall composed of overlapping tangential vanes in said classifying zone immediately below said grinding zone, said wall being of an average diameter slightly larger than the grinding zone, the vanes of said wall being spaced from each other so as to form tangential passages extending inwardly through the wall and directed in the direction of rotation of the rotor, the portion of said rotor enclosed by said wall being provided with at least one constricted radial passage connected to the axial passage of the rotor for receiving classified material and delivering it to said axial passage, a plate mounted on the rotor and extending outwardly therefrom in close proximity to the bottom of said pendant Wall and fan means in the classifying chamber adjacent the annular opening for drawing gaseous fluid through the annular opening into said classifying chamber, additional fan means in said grinding chamber for drawing a limited amount of gaseous fluid through the inlet of said chamber and into the grinding chamber and for distributing the solid material being ground.

9. The apparatus of claim 8 further characterized in that said pendant Wall of tangentially arranged blades is spaced from the wall of the classifying chamber.

10. The apparatus of claim 8 further characterized in that a housing is provided from the top cover plate of the grinding chamber of said housing forming an inlet for gaseous fluid and solid material to be disintegrated.

11. The combination comprising an upright cylindrical casing, upper and lower closures for the upper and lower ends of said casing, said upper closure having an annular inlet therein of lesser diameter than said casing, said lower closure having an axial inlet, a rotor journalled for rotation in said casing, said rotor projecting through and below said axial inlet, an axial channel through the rotor from a position within said casing and terminating on the surface of the rotor outside said casing, an inlet fan on the rotor within the casing and adjacent the axial inlet for moving gaseous fluid through said axial inlet and into the casing, said rotor being provided with a plurality of spaced circumferential fins within said casing and adjacent the upper closure forming radial slots in the rotor, said slots extending into and connected to the channel of the rotor, restrictions in the slots adjacent their junction with the channel of the rotor, a cylindrical pendant wall connected to the upper closure and circumscribing the annular inlet of said closure, said pendant wall being provided with inlets directed inwardly therethrough in the direction of rotation of the rotor, said pendant wall extending substantially throughout that part of the rotor having circumferential fins thereon, at least one port in the cylindrical casing between the upper and lower closures, and means for withdrawing gaseous fluid of the casing through said rotor slots and channel of the casing.

12. The apparatus of claim 11 further characterized in that the rotor is provided with a divider ring extending outwardly in close proximity to the termination of the pendant wall.

13. The apparatus of claim 11 further characterized in that a recirculating fan blading comprising a plurality of radial vanes is provided within the casing between the inlet fan and said spaced circumferential fins.

14. The apparatus of claim 11 further characterized References Cited in the file of this patent in thatf tl'tie rotgr is prtovidedL with a fan hubgnhthjatbpor- UNITED STATES PATENTS ion 0 1 s sur ace ex enor o e casing, sa1 u eing provided with spaced radial channels connected to the S a IV} JJune g axial channel of the rotor and a fan housing is provided 5 2200822 i ey oore 1 2 around said fan hub, said housing being spaced from the 2329208 i S ay 3 lower closure of the cylindrical casing. 2350737 y en g 1944 15. The apparatus of claim 11 further characterized 2359911 3 1 44 in that the spaced circumferential fins are stacked closely 2552565 adjacent each other in slightly spaced relation and means 10 es eaux 9 is provided for clamping the stack of fins into a rotative unit on the rotor. 

